While washing my 500 the other day I noticed some mild dry wall cracking on the side walls and the treads. The tires are 5 years old now and seem to have another 10000 miles left on them easy (10800 on them now). How much longer should I use them? When I replace the tires should I also replace the tubes? Sorry I am not use to dealing with motorcycle tire issues. Mechanical ones are more in my line, lol.